The present invention relates to a diagnosis system using an acoustic emission technique (hereinafter abbreviated to "AE technique"), and more particularly, relates to a rotating machinery diagnosis system with an AE technique, which has a function for judging factors causing mechanical abnormality of a rotary machine.
Accidents happening during the operation of rotary machines, such as steam turbines, electric generators, water turbines, rolling mills, and so on, are likely to lead to serious affairs. Particularly, mechanical accidents of rotating parts are dangerous. In order to prevent such accidents from occurring, it is necessary to detect abnormality in its early stages.
AE techniques have been proposed as one of means for detecting abnormality in its early stages. According to these AE techniques, an ultrasonic signal is detected by an AE sensor mounted on a part of a rotary machine and subject to signal processing. For example, as a method of rubbing monitoring, abnormality is detected through the process that the detected ultrasonic signal is passed through a filter to obtain a rotational component of the signal after the signal has been subject to envelope detection-processing, as disclosed, for example, in U.S. Pat. No. 4,478,082. Another example of the AE techniques is known as diagnosis of journal bearing damage, as disclosed in U.S. Pat. No. 4,481,819.
The prior art abnormality detection systems are useful in detecting abnormal conditions one by one. However, the prior type systems are not useful in detecting a plurality of kinds of abnormality.